The present invention relates generally to a removable stent and an assembly for its delivery or removal from a target site. The present invention particularly relates to a removable stent and system for its use in a medical procedure involving blood vessels, ducts, treatment of enlarged prostate gland, coronary artery disease and the like.
Stents are used in a wide variety of medical procedures where the permanent expansion of an occluded vessel is desired. Usually, stents are constructed of a metal cylinder that is implanted into a patient at the site of obstruction. In a patient suffering from an occluded vessel, balloon catheterization or balloon angioplasty is often the prescribed treatment. However, following such a procedure, restenosis or re-narrowing of the occluded tissue often occurs. Therefore, stents were developed and are used to optimize and improve the initial and long-term outcome in patients treated for an obstructed vessel. In addition to obstructions, stents are also used to provide support for a graft during healing of reconnected vessels. Diseases most often treated using a stent include coronary artery disease, benign prostatic hyperplasia (also referred to as an enlarged prostate gland), and other medical indications where expansion of a lumen, vessel or duct is desired. As such, a variety of stent systems have been developed for medical use. See, for example, U.S. Pat. Nos. 5,100,429; 4,762,128; and 4,800,882.
Although the development of stents for use in medical procedures has been a major advance in treating a narrowed lumen, a variety of complications can and do occur in connection with either the delivery of the stent or, at a later time, following deployment of the stent in vivo. Such problems or complications include failure of proper deployment of the stent, misalignment, dislodgement, or damage of the stent after it is deployed, or re-occlusion of the vessel over time once the stent is inserted. In these cases, removal of the stent is desired. Devices and/or assemblies allowing for the extraction of a stent are known and include, for example, U.S. Pat. Nos. 5,474,563; 5,624,450 and 5,411,507. In particular, Hendrik, U.S. Pat. No. 5,624,450 describes an assembly for the removal of an implanted stent. The assembly entails use of an expandable element having an adhesive outer surface. The expandable element is connected to a pulling device. Insertion followed by expansion of the expandable element inside the faulty stent causes its attachment (adhesion) to the inner surface of the stent allowing the user to then xe2x80x9cpullxe2x80x9d the stent out. A particular disadvantage in this system is that it is unreliable, as attachment of the expandable element to the stent occurs by adhesion. As a result, a more reliable and effective removal system is desired.
An example of an additional stent removal system may also be found in U.S. Pat. No. 5,474,563, which describes a system for removal of a cardiovascular stent device from a blood vessel. The system includes a self-expanding elastomeric stent and an extraction catheter for removal of the cardiovascular stent. The extraction catheter is especially designed so as to specifically engage with projections located on the stent. Removal of the stent occurs by engaging the extraction catheter with the projections. One disadvantage of this extraction system and other similar systems is the requirement for complex extraction instrumentation as well as specific and intricate maneuvering by the physician to engage the extraction tool with the stent.
The above-described removal systems (and other similar devices not specifically described) offer advantages, including effectiveness and safety to both the user and the patient. However, it has been discovered that an obstacle or disadvantage to such devices is that their use is complicated. Additionally, even with the more simple removal systems, the susceptibility of separation of the removal device from the stent during use result in major limitations to the reliability of these systems.
In view of the above, it is apparent that there is a need to provide a removable stent and a system which allows for reliable and minimally traumatic removal of a stent from an in vivo target site. There is also a need to provide a removable stent and system that is efficient, simpler to use for the physician and easy to maneuver in vivo. A reliable and efficient removal system would reduce the overall procedure time required, reduce possible trauma to the lumen wall during use, and therefore reduce patient discomfort during recovery. Such removal systems include properties that reduce the amount of effort required by the physician prior to and during use of the system as well as properties that ensure the system remain intact during removal of the stent.
In view of the foregoing, it is an object of the present invention to provide a removable stent device that addresses the limitations and disadvantages associated with prior removal devices, yet meets the needs of the users.
A further object of the invention is to provide a removable stent system that is efficient, requires minimal effort by the user and that is reliable.
Still another object of the invention is to provide a removable stent assembly having a collapsing element configured around the circumference of the stent so as to allow retrieval of the stent by collapsing one end of the stent to a smaller diameter.
A further object of the invention is to provide a stent removal system where removal of the stent can be achieved by use of a simple removal tool having a grasper attachment. In one aspect of the invention, a stent removal system for removing a stent from a target site in a patient is disclosed. The system can include a removable stent that is collapsible at a proximal end by engagement of a collapsing element with a removal tool. The collapsing element can be a lasso or a discontinuous lasso configured so as to collapse the proximal end of the removable stent for removal from a body site. Alternatively, the collapsing element can be a hook that is movable between an up and a down position. The removal tool is configured so as to allow coupling to the collapsing element of the removable stent. The removal tool can be configured as a tube having a slot at one end allowing for its coupling to the collapsing element. The stent removal system can also include a grasper element designed to aid in the removal of the stent by attachment to a removal tool or a delivery tool.
An additional object of the invention is to provide a method of removing a stent in vivo using a stent removal system.
These and other objects not specifically enumerated herein are believed to be addressed by the present invention which contemplates a stent removal system for removing a stent from a body site that includes a removable stent having a collapsible proximal end, a collapsing element and a removal tool.